Aggregate Testing Definition

10% Fine Value

This test is a measure of the strength of aggregate, which will normally be used in making concrete. It involves compression in a mould of a known mass of aggregate of single particle size and measuring the load required to reduce 10% of the particles to fine material.

Alkali Aggregate Reactivity

This test method permits detection of the potential for deleterious alkali-silica reaction (ASR) of specific cement-aggregate combinations.
The mortar bars are kept in an environment most likely to produce an ASR reaction and their length change is measured over time.
ASR is caused when certain aggregate types expand, and thus, cause cracking in concrete, when in contact with the alkaline environment of the cement paste.

Alkali Reactivity – Chemical

This test method covers chemical determination of the potential reactivity of an aggregate with alkalis in Portland cement concrete, as indicated by the amount of reaction during 24 hours at 80°C between 1N sodium hydroxide solution and aggregate that has been crushed and sieved to pass a 300µm sieve and retained on a 150µm sieve.
ASR is caused when certain aggregate types expand, and thus cause cracking in concrete, when in contact with the alkaline environment of the cement paste.

Alkali Reactivity

This test method covers chemical determination of the potential reactivity of an aggregate with alkalis in Portland cement concrete, as indicated by the amount of reaction during 24 hours at 80°C between 1N sodium hydroxide solution and aggregate that has been crushed and sieved to pass a 300µm sieve and retained on a 150µm sieve.
ASR is caused when certain aggregate types expand, and thus cause cracking in concrete, when in contact with the alkaline environment of the cement paste.

Chloride Content

The total chloride content of aggregate is usually measured to assess whether the aggregate's contribution to the total chloride content of a concrete mix will be low enough to prevent the early onset of corrosion of any embedded steel reinforcement.
The test can be conducted in a variety of chemical means, from approximate dip-stick measures through to potentiometric methods. The usual method is by titration..

Clay Lumps and Friable Particles

This test is used to derive the percentage by mass of friable particles and clay lumps in aggregates, which are to be used for making concrete. The method involves weighing the specimen, then removing clay lumps by soaking and gentle manual abrasion, followed by are-weighing the sample.
Limiting values of clay lumps and friable particles are normally included in concrete specifications, to avoid their deleterious properties on concrete.

Clay Slit and Dust Ppassing/ Sieve

This test is used to derive the percentage by mass of clay, silt and dust in aggregates, which are to be used for making concrete. The method involves weighing the specimen, then removing such material by wash sieving, followed by re-weighing the sample.
Limiting values of clay, silt and dust content are normally included in concrete specifications to avoid their deleterious properties on concrete.

Compaction Fraction

This test is used to derive the compaction percentage of an aggregate when loose compared to the same aggregate compacted in a standard manner. It is useful in assessing an aggregate’s likely compactive state when placed loosely, for example, as a pipe surround material. Aggregate suitable for use as pipe bedding would display a low compaction fraction, indicating it reaches a state of near full compaction under loose placement.

Crushing Value

This test is a measure of the strength of aggregate, which will normally to be used in making concrete. It involves standard compression of 400kN in a mould of a known mass of aggregate of single particle size and measuring resulting percentage of crushed particles.

Drying Shrinkage

Some aggregates change volume considerably from the wet to the dry state and this may affect the concrete in which they are incorporated. The drying shrinkage of concrete containing such aggregate can be as much as four times greater than that of concrete made with non-shrinkable aggregates.
To determine the drying shrinkage of the aggregate under test, it is mixed with cement and water, and cast into prisms of specified dimensions. The prisms are subjected to wetting followed by drying and the change in length from the wet to dry state determined.

Flakiness and Elongation Index

These tests are used to determine the percentage of unsuitably shaped particles for aggregate to be used in concrete.
Aggregate particles are classified as flaky when they have a thickness of less than 0.6 of their mean sieve size, and are classified as elongated when they have a length of more than 1.8 of their mean sieve size.
The index for each type of particle is found by separating the particles and expressing their mass as a percentage of the mass of the sample tested.

Impact Value

This test is used to determine an aggregate’s resistance to impact, usually to assess its suitability for inclusion in concrete.
A sample of single sized aggregate of known mass is subjected to repeated standard impact blows. The mass of particles reduced to a stated size due to the force of impact is then measured, and is expressed as a percentage of the original mass of the sample.

Lightweight Pieces

This test is used to determine the percentage of lightweight pieces in aggregate, usually to assess its suitability for inclusion in concrete.
The test is conducted by means of sink-float separation in a heavy liquid of suitable specific gravity. A heavy liquid with a specific gravity of 2.0 is used to separate particles, which may be classified as coal or lignite. Heavier liquids may be used to check the percentage of other lightweight particles such as shale.

Los Angle Abrasion

This test is used as a measure of degradation of aggregate of standard grading resulting from a combination of actions including abrasion or attrition, impact, and grinding in a rotating steel drum containing 12 steel spheres. As the drum rotates, a shelf plate picks up the sample and the steel spheres, carrying them around until they are dropped to the opposite side of the drum, creating an impact-crushing effect. After the prescribed number of revolutions, the contents are removed from the drum and the aggregate portion is sieved to measure the degradation as percent loss.

Organic Impurities Effect on Mortar Strength

This test would normally be used when a rapid assessment of organic impurities by ASTM C40 indicates their presence. Comparison is made between compressive strengths of mortar made with washed and unwashed fine aggregate.
A reduction in compressive strength of mortar used with unwashed aggregate when compared to the washed aggregate would indicate that the organic impurities are having an adverse affect.

Organic Impurities

This test method covers procedures for an approximate determination of the presence of injurious organic impurities in fine aggregate that are to be used in hydraulic cement mortar or paste. The principle value of this test is to serve as a warning that an aggregate may contain organic impurities and should be investigated further.
It involves comparing the colour of the supernatant of the sample when mixed with sodium hydroxide to that of a standard solution.

Particle Size Distribution

This test method covers the determination of percentile quantity of particles of known diameter within a sample. The specimen can be either passed through a set of standard sieves in its natural state, or if a significant amount of binding material is present, such as clay, then the sample can first be washed over a small aperture sieve to remove the binding material.
The analysis of particle size is useful in assessing the aggregate’s suitability for making concrete.

Sand Equivalent Value

This test is intended to serve as a rapid field test to show the relative proportions of fine dust or clay- like material in aggregate.
This test is useful for rapid assessment when either time or facilities available do not permit the full method of fine dust content by wash sieving.
Limiting values of clay, silt and dust content are normally included in concrete specifications, to avoid their deleterious properties on concrete.

Soundness

This test method covers the testing of aggregates to estimate their soundness when subjected to weathering action in concrete or other applications. This is accomplished by repeated immersion in saturated solutions of sodium or magnesium sulphate followed by oven drying to partially or completely dehydrate the salt precipitation in permeable pore spaces. The internal expansive force, derived from the re-hydration of the salt upon re-immersion, simulates the expansion of water on freezing.

Specific gravity and water absorption

These tests are used to determine density of aggregate particles and their water absorption properties. Both these values are important when designing a concrete mix using these aggregates.
Specific gravity values are obtained by using water displacement methods in saturated aggregate. Water absorption values are obtained by weighing aggregate samples before and after soaking in water.

Sulphate Content

The total Sulphate content of aggregate is usually measured to assess whether the aggregate's contribution to the total Sulphate content of a concrete mix will be low enough to prevent any deleterious effects.